Solvents and novel electrolytic compositions having a large range of stability and high conductivity

ABSTRACT

The present invention is concerned with novel polar solvents and novel electrolytic compositions comprising such solvents, and having a high range of stability, as required for applications in the field of electrochemistry. The present solvents have a highly polar amide function, and preferably combine with a salt soluble in the solvent and having an anion with a delocalized charge, and at least one polymer, to form an electrolytic composition.

FIELD OF INVENTION

The invention concerns new polar solvents and new electrolyticcompositions comprising the same, and having a large range of stability,as required for applications in the field of electrochemistry.

BACKGROUND OF THE INVENTION

Polar aprotic solvents such as cyclic or linear carbonates, or ethersused alone or in mixtures, are known in various electrolyticcompositions. The stability of these products towards highly negativepotentials, close to those of alkaline metals, or highly positive (≧4Vwith respect to Li⁺/Li°), are not satisfactory, and lithium batteriescontaining electrolytes obtained from the dissolution of a lithium saltin these solvents create serious safety problems. Products of the amidetype, whether linear or cyclic, such as dimethylformamide orN-methylpyrrolidinone, possess excellent properties as solvents, but areoxidized at potentials that are still lower, in the order of 3.7 V withrespect to Li⁺/Li°.

Numerous materials of positive electrodes, such as mixed oxides oftransition metals and lithium work under potentials near 4 V withrespect to Li⁺/Li°and therefore require electrolyte stabilitiessignificantly higher than that value. For example, products likeLi_(1−y)Co_(1−x−z)Ni_(x)Al_(y)O₂ wherein x+y≦1 and z≦0.3); manganesespinels Li_(1−α)Mn_(2−x)M_(x)O₄.Li_(1−α)Co_(1−x−y)Ni_(x)Al_(y) wherein0≦x+y≦1; 0≦y≦0.3; 0≦α≦1 and M=Li, Mg, Al, Cr, Ni, Co, Cu, Ni, Fe.

U.S. Pat. Nos. 4,851,307 and 5,063,124 describe electrolytes comprisinga salt, a solvating polymer and an aprotic sulfamide of the generalformulaR¹R²NSO₂R³R⁴wherein R¹, R², R³ and R⁴, the same or different, are independentlyselected from C₁₋₁₀alkyl or C₁₋₁₀oxaalkyl. An example of the product ofthat group is the tetraethylfulfamide (R¹=R²=R³=R⁴=C₂H₅). Thesematerials have increased stability towards reducing or basic agentspresent and having potentials near those of alkaline metals. However,they are oxidized at potentials between 3.8 and 4V with respect toLi⁺/Li°.

EP 0 339 284 discloses dielectric and insulating compounds likeperfluoro-acylamides or perfluoro-sulfonamides R_(F)CONA¹A² andR_(F)SO₂NA¹A², wherein A¹ and A² are alkyl groups. The proposed use ofthese products in capacitors implies that the materials are notconductive and that the impurities and inevitable contaminants,particularly ionic products, are not inducing significant conductivity.

The publication of Sartori et al. in an abstract of a meeting of theElectrochemical Society, Volume 97-1, May 1997, describes certainsulfonamides that could be used as electrolytes in a battery or in anenergy storage system.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided novel polarsolvents and novel electrolytic compositions comprising the same andhaving a high degree of stability, as required for applications in thefield of electrochemistry. More specifically, the solvents of thepresent invention are of the general formulaR¹R²NX(Z)R⁷whereinX=C or SO;Z=O, NSO₂NR₃R₄ or NCN;R¹ et R² are the same or different and are C₁₋₁₈alkyl, C₁₋₁₈ oxaalkyl,C₁₋₁₈ alkylene or C₁₋₁₈oxaalkylene;R³ a R⁶ are the same or different and are C₁₋₁₈alkyl or C₁₋₁₈ oxaalkyl;R⁷ is R_(F), R_(F)CH₂O—, (R_(F))₂ ₂CHO—, (R_(F)CH₂)₂N— or NR⁵R⁶;R_(F) is fluorine, C₁₋₄alkyl, C₁₋₄oxaalkyl or C₁₋₄azaalkyl wherein thealkyl chain is preferably essentially fluorinated and partlychlorinated,with the provisos that:1) if Z=O, then R_(F) is not C₁₋₄alkyl; and2) if Z=O and X=SO, then R5 or R6 is not C₁₋₄alkyl or C₁₋₄oxaalkyl.

The expression “essentially fluorinated” means that the degree offluorination in the chain is sufficient to provide properties similar tothose obtained with a chain entirely perfluorated, such as a hydrophobiccharacter and properties of attracting electrons. Preferably, at leasthalf of the hydrogen atoms of the chain are replaced by fluorine atoms.The expression “partially chlorinated” means that within the essentiallyfluorinated products, the hydrogen atoms remaining are at leastpartially replaced with chlorine atoms.

DETAILED DESCRIPTION OF THE INVENTION

In the present invention, materials with a highly polar amide functionare used for preparing electrolytic compositions useful forelectrochemical applications. It has unexpectedly been found that groupsstrongly attracting electrons, when combined with the amide function,allow the maintenance of solubilizing power towards ionic products,particularly those having a highly delocalized anionic charge, and thusinducing high ionic conductivities. By adding a polar polymer to thesecompositions, there is obtained electrolytes with mechanical propertiesallowing the fabrication of films for use in electrochemical devices,and increasing the security when in operation. Depending on the amountof polar solvent and polymer in the electrolytic compositions, theconsistency thereof can be adjusted to a gel or a plasticized polymer.Further, the polymers can be reticulated to improve mechanicalproperties.

The electrolytic compositions of the present invention have higherstability when compared to materials of the prior art, particularly atvery anodic potentials, especially those exceeding 4 V with respect toLi⁺/Li°.

Preferred low energy reticular salts that are soluble in the polarsolvents of the present invention to form conductive solutions comprisethose having a delocalized charge, such as I⁻, ClO₄ ⁻, BF₄ ⁻, PF₆ ⁻,AsF₆ ⁻, SbF₆ ⁻, R_(F)SO₃ ⁻, XSO₂NSO₂X′⁻, (XSO₂)(X′SO₂)(Y)C⁻ and mixturesthereof, wherein

X and X′ is R_(F), R_(F)CH₂O—, (R_(F))₂CHO—, (R_(F)CH₂)₂N—, R⁸, R⁹R¹⁰N—,with the proviso that at least one X or X′ is R_(F), R_(F)CH₂O—,(R_(F))₂CHO—, (R_(F)CH₂)₂N—;

Y=R_(F), R_(F)SO₂ or CN;

R_(F) is as defined above; and

R⁸ to R¹⁰ are the same or different, and are C₁₋₁₈alkyl or —C₁₋₁₈oxaalkyl.

R_(F) and R⁸-R¹⁰ can be part of a molecular chain. Also preferred areanions derived from 4,5-dicyano-1,2,3-triazole,3,5-bis(RF)-1,2,4-triazole, tricyanomethane, pentacyanocyclopentadieneand pentakis(trifluoromethyl)cyclopentadiene and anions derived fromcyanamide and malononitrile, i.e., R_(F)SO₂NCN⁻, C(CN)₃ ⁻,R_(F)SO₂C(CN)₂ ⁻. Preferred cations comprise those derived from alkalinemetals, more preferably lithium, alkaline earth metals, and organiccations of the “onium” type, such as ammonium, imidazolium, sulphonium,phosphonium and oxonium.

With respect to the electrolytic compositions of the present invention,they include those containing at least one polar solvent as definedabove in combination with one or more polar molecules acting as aco-solvent. Such other polar molecules include solvents capable offorming compatible mixtures, such as dialkyl ethers of ethylene glycol,diethylene glycol, triethylene glycol, polyethylene glycols preferablyhaving a mass of from 400 to 2000; or esters, preferably carbonic acidesters, whether linear or cyclic, such as dimethylcarbonate,methylethylcarbonate, diethylcarbonate, ethylene carbonate, propylenecarbonate, or esters such as γ-butyrolactone, nitriles such asglutaronitrile, or 1,2,6-tricyanohexane. These other polar molecules, orco-solvent, can be added alone or in mixtures to the solvent of thepresent invention. An example of the preferred mixture is ethylenecarbonate with a dialkyl ether.

The present invention further includes solid electrolytes obtained bythe addiiton of the polymer to a solvent or solvent-co-solvent mixturecontaining at least one salt as defined above in solution. The amount ofpolymer can be selected so that the solvent acts as a plasticizing agentof the polymer, i.e. in concentration of 3 to 30% by weight, preferablybetween 10 and 25% by weight. Preferred polymers for such compositionsare those with monomer units containing solvating units, such as thosederived from ethylene oxide, propylene oxide, epichlorohydrine,epifluorohydrine, trifluoroepoxypropane, etc. To obtain a gel, theamount of solvent and salt in the composition should be between 30 and95% by weight, preferably between 40 and 70%. In addition to thepolymers listed above, those containing units derived fromacrylonitrile, methylmethacrylate, vinylidene fluoride,N-vinylpyrolidinone are also preferred, and can be either homo- orcopolymers, such as vinylidene fluoride and hexafluoropropenecopolymers. A copolymer containing from 5 to 30% molar ofhexafluoropropene is particularly preferred. In a variation, thepolymers are polyelectrolytes incorporating anions with a delocalizedcharge in the macromolecular woof. In such conditions, negative chargesare immobilized and only positive counter-charges participate in theionic conduction process.

The present electrolytic compositions can be used wherever a highstability is required, particularly when oxidation or highly positivepotentials are present. A good example is an electrochemical generatorwherein it is advantageous to have a high electromotive force,particularly in generators containing lithium ions. In such systems, thenegative electrode comprises metallic lithium, one of its alloys, acarbon derivative, preferably petrolium coke or graphite, an oxide witha low potential of intercalation such as titanium spinelsLi_(2x+1+3y)Ti_(x+5)O₁₂ (x≧0 and y≦1), a double nitride of a transitionmetal and lithium such as Li_(3−x)Co_(x)N, or having an antifluoritetype structure such as Li₃FeN₂ or Li₇MnN₄.

The materials for the positive electrode comprise intercalationcompounds, polydisulfides or oxocarbones. Intercalation compoundsinclude vanadium oxide, and preferably those with the formula VO_(x)wherein 2≦x≦2.5; LiV₃O₈; cobalt and lithium mixed oxides of the generalformula Li_(1−α)Co_(1−x−y)Ni_(x)Al_(y) wherein 0≦x+y≦1; 0≦y≦0.3; 0≦α≦1;partly substituted manganese spinels of the general formulaLi_(1−α)Mn_(2−z)M_(z)O₄ wherein 0≦z≦1 and M=Li, Mg, Al, Cr, Ni, Co, Cu,Ni, Fe; and double phosphates of the olivine or Nasicon structure suchas Li_(1−α)Fe_(1−x)Mn_(x)PO₄, Li_(1−α+2x)Fe₂P_(1−x)S_(x)O_(4′) whereinx≧0 and α≦1. Oxocarbones electrode materials are preferably rhodizonicacid salts; polydisulfides including derivatives resulting from theoxidation of dimercaptoethane, 2,5-dimercapto-1,3,4-thiadiazole,2,5-dimercapto-1,3,4-oxaadiazole, and1,2-dimercaptocyclobutene-3,4-dione.

Electrochemical generators using the present electrolytic compositionspreferably contain solid electrolytes, either plasticized or gelled. Ina preferred embodiment of the invention, at least one of the electrodesis a composite comprising the electrode materials in a mixture with theelectrolytic composition and carbon such as Shawinigan® black,Ketjenblack®, or graphite.

Another application of the invention is that of supercapacitors whereinat least one electrode comprises high surface area carbon, and theelectrical energy is stored as a result of the capacity of the doublelayer between the carbonated material and the electrolyte. In apreferred embodiment, the two electrodes are symmetrically built withcarbon having high surface area, and this material is mixed with theelectrolyte to form a composite. Another possibility is to use theelectrode material containing at least one polymer having conjugateddouble bonds. In a preferred embodiment, the conjugated polymer may havethree degrees of oxidation, obtained by reduction (“n” doping)concomitant to an injection of electrons and cations, or by oxidation(“p” doping) concomitant to an electron extraction and anion injections,from the neutral form. Polymers comprising phenyl-3-thiophene, andparticularly poly(4-fluorophenyl-3-thiophene) are preferred.

The following examples are provided to illustrate the preferredembodiments of the present invention, and should not be construed aslimiting its scope.

EXAMPLE 1

Trifluoroethanol (18.2 mL, 25 mml) dissolved in 100 mL of ether areadded to 7 g of sodium hydride. When no more hydrogen gas evolves, thesolution is centrifuged and the supernatant clear liquid is added at 0°C. to 35 μg (25 mml) of dimethysulfamoyl chloride dissolved in 100 mL ofdry ether under stirring. A white precipitate of NaCl forms and thereaction is completed in two hours. The slurry is filtered and the etherstripped in a rotary evaporator. The residue is diluted with 50 ml ofdichloromethane and washed with 10% HCl in water. The organic layer isseparated, dried with anhydrous magnesium sulfate. The correspondingtrifluoethyl-N,N dimethylsulfamate is distilled under reduced pressure.RMN: ¹⁹F: triplet δ=74.7 ppm, J_(HF)=8.1 Hz; ¹H: quartet δ=4.66 (2H),singlet δ=3.6 (6H). The conductivity of the lithium salts of thebis(trifluoromethanesulfonimide) (CF₃SO₂)₂NLi in solution in thissolvent is provided in Table 1 with respect to several concentrations.TABLE 1 molality (mol · kg⁻¹) conductivity κ_(sp) (S · cm⁻¹) 0.265 0.6340.506 0.922 0.898 1.025 1.160 0.796

The range of electrochemical stability is measured by cyclic voltametryon a platinum microelectrode (15 μm diameter) for anodic potentials, andnickel for cathodic potentials. The stability range is from 0 to 5.2 Vvs. Li+/Li°. The variation of conductivity with respect to thetemperature is found is Table 2 for a concentration of 0.898 mol·kg⁻¹.TABLE 2 T (° C.) κ_(sp) (S · cm⁻¹) T (° C.) κ_(sp) (S · cm⁻¹) 14.900.753 30.29 1.203 14.92 0.7550 35.39 1.415 19.93 0.882 40.81 1.657 25.111.030

EXAMPLE 2

107.4 mL of dimethylsulfamoyl chloride are heated under reflux andnitrogen atmosphere with 70 g of potassium fluoride and 10 mL of water.The mixture is cooled and extracted with dichloromethane, dried withmagnesium sulphate, and distilled. The compound obtained, (CH₃)₂NSO₂F,has a dielectric constant greater than 30. The range of stability, asdetermined by cyclic voltametry, is 5 V vs. Li+/Li°. The lithium salt ofthe fluorosulfonimide, (FSO₂)₂NLi is soluble in this medium, and itsconductivity at 25° C. is greater than 1 mScm⁻¹ for concentrationsbetween 0.5 and 1 mole·kg⁻¹.

EXEMPLE 3

1.6 g of sodium hydride are added to 6.3 mL of1,1,1,-3,3,3,-hexafluoropropanol dissolved in 25 ml of anhydrous ether.When no more hydrogen gas evolves, the solution is centrifuged, and 8.6μg (60 mml) of dimethylsulfamoyl chloride dissolved in 25 mL of dryether are added to the supernatant liquid under agitation at atemperature of 0° C. A white precipitate of sodium chloride is thenformed et the reaction is completed after 2 hours. The slurry isfiltered and the ether is evaporated with a rotary evaporator. Theresidue is placed in 20 mL of dichloromethane and washed with an aqueoussolution of 10% hydrochloric acid. The organic phase is separated anddried with anhydrous magnesium sulphate. The hexafluoropropyleN,N-dimethylsulfamate is obtained by evaporating the dichloromethane anddistilled under reduced pressure. The compound has a dielectric constantgreater than 20, and the conductivity of solutions of salts ofbis(trifluoromethanesulfonimide) (NC₂H₅)₄(CF₃SO₂)₂N in this solvent arebetween 5×10⁻⁴ and 2×10⁻³ Scm⁻¹ at 25° C. in concentrations varying from0.2 to 1 mole·kg⁻¹.

EXAMPLE 4

4.2 g of cyanamide and 11.22 g of diazabicyclo 2,2,2-octane (DABCO) areadded to 15.76 g of ethylmethylsulfamoyl chloride dissolved in 100 mL oftetrahydrofuran. After agitating the mixture at room temperature for 8hours, 13 g of oxalyl chloride dissolved in 40 mL of anhydroustetrahydrofuran are added dropwise. After gas emissions have stopped (COand CO₂), the DABCO chlorohydrate is filtered and remaining THF isevaporated under reduced pressure. The solid is then placed in 50 mL ofacetonitrile to which is added 12.2 g of ethylmethylamine at 0° C. Theethylmethylammonium chloride thus obtained is separated and the solventis evaporated under reduced pressure. The polar product

The polar product is solubilized in dichloromethane, and washed withwater containing 2% hydrochloric acid, and subsequently 5% sodiumbicarbonate. Following removal of dichloromethane, the compound isdistilled under reduced pressure. This product can be used as a solventfor delocalized anions salts, particularly perfluorinated imides.

EXAMPLE 5

33 g of 1,1-dimethylsulfamide (CH₃)₂SO₂NH₂ and 6 g of caustic soda in200 mL of water are heated to reflux for 2 hours. The reaction product,the sodium salt of bis(dimethylaminosulfonimide), i.e.,Na[N(SO₂N(CH₃)₂)], is obtained by evaporation of the water andrecristallisation in ethanol. 25 g of this salt suspended in 100 mL ofanhydrous are reacted with 9 mL of oxalyl chloride. At then end of thereaction, i.e., no more gas emissions, the slurry is cooled to 0° C. and20.7 mL of diethylamine dissolved in 50 mL of acetonitrile are added.The mixture is then agitated for 4 hours at room temperature, andsubsequently filtered. Any remaining acetonitrile is removed underreduced pressure. The liquid obtained is solubilized in dichloromethaneand washed with water containing 2% hydrochloric acid, and subsequently5% of sodium bicarbonate. The solution is passed through an aluminacolumn and the dichloromethane is evaporated under reduced pressure. Thepolar solvent

is kept anhydrous by adding lithium hydride.

EXAMPLE 6

An electrochemical generator comprising a negative electrode of lithiumof 25 μm on a nickel support of 10 μm, a positive electrode compositecontaining 78% by weight of vanadium oxide V₂O₅, 8% of carbon black(Ketjenblack®) and 14% of a vinylidene fluoride-hexafluoropropenecopolymer on a nickel collector (10 μm) has been prepared. The positiveelectrode capacity thus obtained by spreading from a cyclohexanonesuspension, is 2.8 mAh/cm². The electrolyte comprises a solution of 0.15M·kg⁻¹ of Li(CF₃SO₂)₂N in the polar compound of Example 1 in apolypropylene porous separator of the Celgard® type. The generator wascycled over 150 cycles between 1.6 et 3.4V at C/3.7 while maintaining aratio of charge and discharges capacities equal to 1 and a use rateof >75% over 30 cycles. The ohmic drop remained between 20 and 120 mV.

EXEMPLE 7

An electrochemical generator of the “rocking chair” type was preparedwith 2 composite electrodes similar to those of Example 6. Lithium andtitanium spinel Li₄Ti₅O₁₂ was used as the negative electrode, to give asurface capacity of 2.6 mAh·cm⁻². Lithium cobaltite was used for thepositive electrode, to give a surface capacity of 2.4 MAh·cm⁻². Theelectrolyte was prepared in a manner similar to that of Example 6 with asolution of 0.15 M·kg⁻¹ of Li(CF₃SO₂)₂N in the polar compound of Example1 in a polypropylene porous separator of the Celgard® type. Thegenerator was cycled over 500 cycles between 1.5 et 3.3 V a C/4 whilemaintaining a ratio of charge and discharges capacities equal to 1 and ause rate of 80%.

EXEMPLE 8

An electrochemical generator of the supercapacitor type is prepared with2 symetrical composite electrodes of high surface area carbon (680m²·g⁻¹) and nickel fibres on a nickel support, and bound by a vinylidenefluoride-hexafluoropropene copolymer. The electrolyte comprises 75% bywieght of a gel of a molar solution of tetraethylammoniumfluorosulfonimide (C₂H₅)₄N[(CF₃SO₂)₂N] in the same polymer. The systemcapacity is 1.2 F·g⁻¹ over 12 000 cycles performed between 0 and 2.5 V.

EXEMPLE 9

A polymer electrolyte is prepared by plasticizing an ethyleneoxide-allylglycidyl ether copolymer containing the lithium salt ofdimethylaminosulfonyl-trifluoromethane-sulfonimide Li[(CH₃)₂SO₂NSO₂CF₃]with a ratio oxygen from the ether functions of the polymer to lithiumof 14:1 with the polar compound of Example 5 with a weight ratio 65:35.This electrolyte has a conductivity of 10⁻⁴ Scm⁻¹ at 25° C. and anelectrochemical stability range of 0 to 4V vs. Li⁺/Li°. This electrolytecan be reticulated by a free radical source to give elastomers with goodmechanical properties.

While the invention has been described in connection with specificembodiments thereof, it will be understood that it is capable of furthermodifications and this application is intended to cover any variations,uses or adaptations of the invention following, in general, theprinciples of the invention and including such departures from thepresent description as come within known or customary practice withinthe art to which the invention pertains, and as may be applied to theessential features hereinbefore set forth, and as follows in the scopeof the appended claims.

1. An aprotic polar compound having solvent properties and having theformula:R¹R²NX(Z)R⁷ wherein X=C or SO; Z=O, NSO₂NR³R⁴ or NCN; R¹ and R² are thesame or different and are C₁₋₁₈ alkyl, C₁₋₁₈ oxaalkyl, C₁₋₁₈ alkylene,C₁₋₁₈ oxaalkylene; R⁷ is R_(F), R_(F)CH₂O—, (R_(F))₂CHO—, or(R_(F)CH₂)₂N— or R⁵R⁶N—; R³ to R⁶ are the same or different and areC₁₋₁₈ alkyl or C₁₋₁₈ oxaalkyl; R_(F) is C₁₋₄ alkyl, C₁₋₄ oxaalkyl, C₁₋₄azaalkyl, wherein C₁₋₄ alkyl, C₁₋₄ oxaalkyl, C₁₋₄ azaalkyl are eachperfluorinated, with the proviso that if Z=O then R⁷ is not NR⁵R⁶.
 2. Anelectrolytic composition, comprising: at least one aprotic polarcompound having solvent properties and having the formula:R¹R²NX(Z)R⁷ wherein X=C or SO; Z=O, NSO₂NR³R⁴ or NCN; R¹ and R² are thesame or different and are C₁₋₁₈ alkyl, C₁₋₁₈ oxaalkyl, C₁₋₁₈ alkylene,C₁₋₁₈ oxaalkylene; R⁷ is R_(F), R_(F)CH₂O—, (R_(F))₂CHO—, or(R_(F)CH₂)₂N— or NR⁵R⁶; R³ to R⁶ are the same or different and are C₁₋₁₈alkyl or C₁₋₁₈ oxaalkyl; R_(F) is a fluorine atom, C₁₋₄ alkyl, C₁₋₄oxaalkyl, or C₁₋₄ azaalkyl, wherein C₁₋₄ alkyl, C₁₋₄ oxaalkyl, C₁₋₄azaalkyl are each perfluorinated, with the proviso that if Z=O then R isnot NR⁵R⁶, and a salt soluble in said polar compound having an anionwith a delocalized charge.
 3. The electrolytic composition according toclaim 2, wherein the salt comprises at least one selected from the groupconsisting of I⁻, ClO₄ ⁻, BF₄ ⁻, AsF₆ ⁻, SbF₆ ⁻, PF₆ ⁻, R_(F)SO₃ ⁻,XSO₂NSO₂X′⁻, (XSO₂)(X′SO₂)(Y)C⁻, anionic derivative of4,5-dicyano-1,2,3-triazole, 3,5-bis(RF)-1,2,4-triazole, tricyanomethane,pentacyanocyclopentadiene, pentakis(trifluoromethyl)cyclopentadiene,R_(F)SO₂NCN⁻, C(CN)₃ ⁻, R_(F)SO₂C(CN)₂ ⁻, and mixtures thereof, whereinX and X′ comprise at least one selected from the group consisting ofR_(F), R_(F)CH₂O—, (R_(F))₂CHO—, or (R_(F)CH₂)₂N—, and R⁸, R⁹R¹⁰N—, withthe proviso that at least one X or X′ is R_(F), R_(F)CH₂O—,(R_(F))₂CHO—, or (R_(F)CH₂)₂N—; Y=R_(F), R_(F)SO₂ or CN; R_(F) is afluorine atom, C₁₋₄ alkyl, C₁₋₄ oxaalkyl, or C₁₋₄ azaalkyl, wherein C₁₋₄alkyl, C₁₋₄ oxaalkyl, C₁₋₄ azaalkyl are each perfluorinated and can bepart of a macromolecular chain; and R⁸ to R¹⁰ are the same or different,and are C₁₋₁₈ alkyl or C₁₋₁₈ oxaalkyl.
 4. The electrolytic compositionaccording to claim 3, further comprising at least one cation selectedfrom the group consisting of alkaline metal, alkaline earth metal,organic onium cation, ammonium, imidazolium, sulfonium, phosphonium,oxonium, and mixtures thereof.
 5. The electrolytic composition accordingto claim 3, further comprising at least one lithium cation.
 6. Theelectrolytic composition according to claim 2, further comprsing aco-solvent.
 7. The electrolytic composition according to claim 2,further comprising at least one aprotic, polar co-solvent selected fromthe group consisting of dialkylethers of ethylene glycol, diethyleneglycol, triethylene glycol, polyethylene glycol; carbonic acid ester;γ-butyrolactone; nitrile; tricyanohexane; dimethylformamide;N-methylpyrrolidinone; and mixtures thereof.
 8. The electrolyticcomposition according to claim 2, further comprising at least onepolyethylene glycol co-solvent having a mass ranging from 400 to 2000g/mol.
 9. The electrolytic composition according to claim 2, whichcomprises at least one polymer.
 10. The electrolytic compositionaccording to claim 2, which comprises at least one polymer, wherein thepolymer is a polyelectrolyte comprising a macromolecular chain andhaving a delocalized anionic charge.
 11. The electrolytic compositionaccording to claim 2, which comprises at least one polymer, wherein thepolymer is a homopolymer or copolymer comprising polymerized monomerunits selected from the group consisting of ethylene oxide, propyleneoxide, epichlorohydrine, epifluorohydrine, trifluoroepoxypropane,acrylonitrile, methylmethacrylate, vinylidene fluoride,N-vinylpyrolidinone, hexafluoropropene, and mixtures thereof.
 12. Theelectrolytic composition according to claim 2, which comprises at leastone polymer, wherein the composition is plasticized or in the form of agel.
 13. An electrochemical generator, comprising at least one negativeelectrode, at least one positive electrode, and the electrolyticcomposition according to claim
 2. 14. The electrochemical generatoraccording to claim 13, wherein the electrolytic composition comprises atleast one co-solvent.
 15. The electrochemical generator according toclaim 13, wherein the electrolytic composition comprises at least onepolymer.
 16. The electrochemical generator according to claim 13,wherein the negative electrode comprises at least one selected from thegroup consisting of lithium metal, lithium alloy, carbon intercalationcompound, oxide having a low potential of intercalation, double nitrideof a transition metal and lithium, and mixtures thereof.
 17. Theelectrochemical generator according to claim 16, wherein the carbonintercalation compound is petroleum coke or graphite, and wherein theoxide having a low potential of intercalation is a titanium spinel. 18.The electrochemical generator according to claim 13, wherein thepositive electrode comprises at least one selected from the groupconsisting of vanadium oxide, mixed oxide of lithium and vanadium, oxideof cobalt and lithium, manganese spinel, double phosphate of the olivineor Nasicon structure, salt of rhodizonic acid, polydisulfide derivedfrom the oxidation of 2,5-dimercapto-1,3,4-thiazole,2,5-dimercapto-1,3,4-oxadiazole, 1,2-dimercaptocyclobutene-3,4-dione,and mixtures thereof.
 19. An supercapacitor-type energy storage system,comprising as an electrolyte the electrolytic composition according toclaim 13, at least one polymer, and optionally a co-solvent.
 20. Anelectrochemical device, comprising as an electrolyte the electrolyticcomposition according to claim 2, and optionally a co-solvent,impregnated in one or more porous membranes.